IL32583A - Method and apparatus for producing intertwined yarn - Google Patents

Description

Method and apparatus for producing intertwined yam Gt 30876 This invention relates to a method for whirling the individual filaments of multifilament yarns or threads by means of a flowing medium, the yarn to be treated being guided substantially perpendicularly through to the direction of flow of the medium..

Methods and apparatus are known for producing a tousled or intertwined effect in the individual filaments or multifilament yarns. Thus, apparatus is known which comprises bores, grooves or the like as yarn guides, along whose longitudinal axis the yarn travels. As the yarn travels along guides such as these, a jet of medium under pressure is blown on to it from one or more nozzles, with the result that the individual filaments are irregularly intertwined. The nozzles may be differently arranged.

The filament is guided through the jet under a tension which prevents it from slackening. In addition, at least two vortices are produced in the jet, their axes running parallel to the axis of the filament.

Another apparatus suitable for this type of yarn treatment is described in Canadian Patent Specification 55¾,150. In this case, the filament is guided through a jet which issues from a nozzle and strikes a so-called resonance chamber situated opposite the nozzle opening.

It is thus possible by using the conventional methods and apparatus to obtain a yarn which, despite a relatively small increase in volume, is intertwined or tousled in such a way that it can be further processed without any difficulties. Unfortunately, this advantage is offset by an excessive consumption of the medium under pressure.

A measure of tousling or intertwining is the so-called "opening length" which is defined as the distance by which a needle inserted into the yarn perpendicularly to the axis thereof can be displaced axially of the yarn until the next intertwining point prevents further relative movement between needle and yarn. The shorter the opening length, the greater the extent to which the individual filaments are tousled in the yarn. In cases where conventional methods and apparatus are used, it is noticeable that the opening lengths of filaments which are to be wound up in the usual way following this treatment differ greatly at the beginning and end of winding. In addition appreciable differences are evident in the opening length between successive intertwines.

Another disadvantage of conventional methods and apparatus for intertwining the individual filaments of multifilament yarns by means of a jet of pressurised medium, is that the opening lengths in the finished yarn differ greatly and, above all, cannot be predetermined in regard to their average values. Thus, as a rule it is almost impossible to produce a yarn package in which the average opening length determined from the usually vastly different individual opening lengths remains the same throughout the entire length of yarn wound up.

An object of the present invention is to make it possible to intertwine multifilament yarns of widely variable denier in such a way that the intervals between the intertwines, i.e. the opening lengths, are kept the same or made to differ under control throughout the entire winding operation in a manner comparable to twisted yarn. It is also desired to preadjust both the average opening length and to predetermine the degree of intertwining to a large extent. The invention is preferably carried into effect on a yarn treating apparatus identical with or similar to that described- in Canadian Patent Specification 55^,150.

The invention provides a method for producing an intertwined yarn of predetermined a\rerage opening length as herein defined, in which the yarn to be treated is guided through ajet of a medium directed substantially perpendicularly to the yarn and thereafter flowing freely away, and the yarn is subjected to fluctuations in yarn tension, the frequency of the fluctuations being given by: where n = the number of cycles of fluctuations in tension per minute, w = the rate of travel of the yarn in metres perminute and _1 = the required average opening length as herein defined in metres.

These fluctuations in tension may follow one another at regular or irregular time intervals, depending upon whether it is desired to obtain a regular interval between the intertwines, or a pattern that is controllable in its in more detail in the following, produces close similarity between the individual opening lengths. In this opening length associated with a specific tension cycle always corresponds sufficiently closely to the length of yarn that has passed through the blowing zone or jet during tension cycle. It is mathematically determined by the relation in which _ is the duration of the tension cycle in minutes, whilst the remaining symbols are as defined above.

Tests conducted without fluctuations in tension have shown that the opening lengths in the whirled yarn have individual values differing vastly as a rule from the average opening length as determined statistically on the finished yarn. In contrast, the individual opening lengths are substantially equal within narrow limits when regularly recurring fluctuations in tension are applied to them. When these results are recorded in the form of a curve there is a sharp maximum frequency in the opening length that can be calculated from the frequency of the fluctuations in tension and the rate of travel of the yarn.

Basically, it is possible in accordance with the invention to follow three different procedures: a) A wide maximum around the calculated value for the opening length produces a statistical distribution similar to the Poisson distribution. This is achieved by using jet pressures in the lower range of the limits specified and by employing lower and upper yarn tensions in the lower part of the particular range specified. b) In addition to a well defined maximum in respect of the value calculated for the opening length, the yarn also shows kinks with lengths of up to a few centimetres. A distribution such as this is substantially obtained in cases where w/n is less than about 0.02 m. In addition, a distribution of this kind is obtained in cases where the lower yarn tension in particular is reduced to around zero. c) The third possibility represents the preferred embodiment of the invention with which it is possible to obtain the expected opening length in the treated yarn with high accuracy or, where irregularity is required, to obtain this very irregularity with a high degree of accuracy, providing certain requirements are satisfied, especially in regard to the pressure of the jet and the yarn tension values.

Blowing pressures of from 2.5 to 5 atrns., preferably from 3.2 to 4.2 atms . , are used in cases where air is used as the blowing medium. In cases where other blowing media, for example steam, are used, the initial pressures are corrected in a manner known to any competent expert corresponding to the different blowing velocities governed both by material and physical data. The same applies as regards nozzles differing in form from those described.

The yarn tension fluctuates between a lower range o from 0 2 to 18 d n nd n u er ran e of from 0.4 to 0.8 p/den. The lower tension range is preferably between 0.04 and 0.15 p/den and the upper range preferably between 0.45 and 0.63 p/den.

Although the choice of the frequency of the fluctuations in yarn tension is not critical, technically expedient upper and lower limits arise out of the need for a rational working speed on the one hand and on the other hand, out of the fact that the yarn must follow closely the deflecting movements and the measures ^producing the change in tension without excessive outlay in terms of machinery. In addition, to this, allowance has to be made for the fact that where w/n is smaller than about 0.02 ra. it is not possible to obtain strict consistency between the actual opening length and the calculated opening length. Instead if the actual opening length falls short of the calculated opening length a yarn of the kind covered by possibility b) above is formed.

Accordingly, favourable values for the frequency of the fluctuations in yarn tension lie between about 2000/min and about lOOOO/min and preferably between about 5000/min and about 8500/min, i.e. to between about 33 c/s and about 170 c/s, and preferably between about 83 c/s and about 142 c/s.

.Accordingly, important factors in the process of the invention include take-off rate, the frequency of fluctuation in yarn tension, upper and lower tension range, nozzle dimensions and blowing pressure or blowing velocity and opening pressure. In particular, it has been found that to obtain a sharp maximum frequency the ratio between minimum and maximum yarn tension and also the average value of the two tension ranges must be kept within narrow limits. In this case it is essential to maintain a minimum tension, especially with a lower limit, as well as a maximum tension limited at both ends, in dependence upon the denier of the yarn. Similarly, it is necessary to maintain a narrow pressure range for the blowing medium. It has been found that the same end result can be obtained with the process according to the invention as with conventional processes, despite the lower consumption of air. Another major advantage of the method according to the invention is that it is possible to obtain an intertwined or tousled yarn which, unlike conventional yarns, has a regular distribution of kinks comparable to the regularity of the twist.

The invention is illustrated by the following Exampl In addition, apparatus suitable for carrying out the process according to the invention is discussed with reference to the accompanying drawings.

EXAMPLE 1 A polyester yarn of denier 68/24 den. was treated in a blowing apparatus of the kind described in Canadian PatentSpecification 55^,150 with the following dimensions length of the bloAving duct ' 8,0 mi diameter of «the blowing duct 2.0 mm length of the resonance bore 5.0 mm diameter of the resonance bore 2.0 mm Gap between the opening of the blowing duct and the opening of the resonance bore Gap between the yarn guides in front of and behind the BloAving zone, as seen in the direction o yarn travel diameter of the yarn guides blowing pressure A pin is arranged 30 cm in front of the blowing unit between two yarn guides arranged 15 cm apart, the pin being eccentrically mounted with respect to the line of yarn travel on a disc rotatable about an axis perpendicularly to the direction of yarn travel. The pin serves to deflect the yarn periodically. The eccentric pin was arranged in such a way that the minimum yarn tension obtained was about 8 cp and the maximum yarn tension about 35 cp. The frequency of the changes in yarn tension was adjusted to 7000/min, and the rate of yarn travel was 245 m/min. The opening length was highly regular at 3.5 cm which corresponded exactly to the calculated value: 2¾5 EXAMPLE 2 In an arrangement of exactly the same kind as that of Example 1, an eccentric driven through an interference gear, producing deviations of + 15^ at an average frequency of 7000/min. Examination of the opening lengths revealed an average opening length of 3.5 cm with fluctuations in deflection frequency from the average value of 7000/min.

EXAMPLE 3 With otherwise the same arrangement and procedure as in Example 1, the blowing pressure was varied between 3.5 and 3.9 atms. The opening lengths remained constant at 3.5 cm., although more distinct kinks were obtained as the blowing pressure increased.

EXAMPLE 4 With the same arrangement as that used in the preceding examples, at a constant frequency of 7000/min. and under a blowing pressure of 3.7 atms., both the lower and the upper tension val ues were varied by varying the effective eccentric diameter and also the position of the eccentric or pin acting as the eccentric. Variations in the lower value between 5 and 9 p produced only a slight change in the effect, though the maximum frequency became much more pronounced when the upper yarn tension was increased above about 30 p. The opening length was constant at 3.5 cm^ EXAMPLE 5 The conditions of Example 3 were modified by increasing the upper yarn tension in stages. It was found that when the maximum yarn tension was increased beyond ^O- l p and the lower yarn tension simultaneously lowered to below 5 p, neither a regular distribution of the opening lengths nor one changing with the frequency occurred in a well defined form. At a blowing pressure of from 3.5 to about 3.7 atms., there was a wider variation in the opening lengths with a maximum at around 3«5 cm (case a) .

At a blowing pressure of from about 3.7 to 3.9 atms., there was a pronounced peak at an opening length of 3.5 cm, although very short as well as relatively long opening lengths were noticed (case b).

EXAMPLE 6 Under otherwise the same conditions as in Example 3, a yarn tension of 0 and ¾5 p was alternated periodically. The distribution according to case a was obtained at blowing pressures of from 3.5 to 3.7 atms., whilst the distribution according to case b__ was obtained at blowing pressures from 3.8 to about 4.0 atms.

EXAMPLE 7 Under otherwise the same conditions as in Example 1, the rate of yarn travel was reduced in stages. Up to a yarn travel rate of 140 m/min (l = 140/7000 = 0.02 m), the opening length corresponded exactly to the calculated conditions. When the yarn travel rate was further increased the distribution changed to case b.

The invention will now be further described with reference to the accompanying drawings, wherein: Figure 1 shows different distribution curves for the opening length, the frequency of the particular opening length being plotted against the opening length.

Figure 2 is a diagrammatic illustration of apparatus for carrying out the process according to the invention.

Figure 3 illustrates a known type of nozzle suitable for carrying out the process according to the invention.

In Figure 1, the curve 1 shows the frequency distribution, of the opening lengths in the treatment of a yarn in case a. Curve 2 shows the distribution of the opening lengths in the case of a yarn treated in accordance with the preferred embodiment of the invention, curve 3 shows the frequency distribution of the opening lengths formed in cases where the procedure resulted in case b„ As can be clearly seen, the maxima lie at the calculated place.

Figure 2 diagrammatically illustrates an apparatus for carrying out the process according to the invention.

A multifilament yarn to :be treated, passes yarn guides and 6 which are disposed respectively in front of and behind an eccentric disc 7 which carries a deflector pin 8. The nozzle 9 is of open design. A suitable embodiment is shown by way of example in Figure 3.

Arranged respectively in front of and behind the :blowing zone there are yarn guides 10 and 11 by which the yarn is held in the jet. However, any form of blowing unit which enables the blowing medium to flow off freely from the blowing zone may be used.

The yarn h travels from a delivery means (not shown) arranged in front of the yarn guide 5, through the yarn guide 5, over the deflector pin 8, through theyarn guide 6 of the blowing nozzle 9 and then through another delivery means (again not shown) to a conventional winding mechanism.

The axis of rotation of the eccentric disc 7 is preferably arranged in such a way that it can be displaced perpendicularly of the direction of yarn travel, the axis remaining parallel to its original position. In this way the extent to which the yarn is deflected can be controlled. Instead or in addition, the pin 8 on the eccentric disc 7 m y also be radially adjustable. It is clear that one yarn tension fluctuation cycle or period corresponds to one revolution of the eccentric disc.

Instead of one pin 8, two or more pins 8 may be arranged at regular intervals around the periphery of the eccentric disc. The upper limit to the number of pins is governed by the requirement that no pin 8 must touch the yarn until the preceding pin has ceased to be in contact with the yarn.

Instead of the eccentric referred to, any other known means may be used to produce the fluctuations in yarn tension, such as for example as electromagnetic yarn brake which is cut out and/or is switched on and off in the required rhythm. A vibrator of adjustable frequency may also be used.

The embodiment shown in Figure 3 as an exemplary form of a suitable blowing nozzle has a nozzle body 12 with a blowing duct 13 and, opposite this duct, a second body 14 in which a resonance or compression chamber 15 is arranged. A blowing zone is defined by the common axis of the blowing duct 13 and the compression chamber 15. Two yarn guides 10 and 11 each preferably in the form of a narro.w eye or small tube are arranged just in front of and just behind the blowin zone in such a way that they keep the yarn 4 passing through precisely in the jet of medium. However, the blowing nozzles that may be used for carrying out the process according to the invention are by no means limited to this embodiment.

In fact it is possible to use any type of nozzle that enables the blowing medium to flow off freely from the,, .blowing zone. For example, the resonance or compression chamber 15 may be left out altogether or replaced by a flat plate or any other type of obstacle to flow. The only requirement that has to be satisfied is that the blowing medium should be able to flow off freely from the treatment zone, preferably not, or not only, in the direction, of the general yarn axis. The types of blowing unit characterised in the foregoing are referred to in the present context as "nozzles of open design".

The means used to generate the fluctuations in yarn tension must be arranged between the delivery means (not shown) disposed on either side of the nozzle 9. They may be arranged in front of or behind the nozzle 9, as seen in the direction of yarn, travel.

Claims (16)

WHAT WE CLAIM IS:

1. A method for producing an intertwined yarn of predetermined average opening length, as herein defined in which the yarn to be treated is guided through a jet . of a medium directed substantially perpendicularly to the yarn and thereafter flowing freely away, and the yarn is subjected to fluctuations in yarn tension, the frequency of the fluctuations being given by: where n = the number of cycles of fluctuations in tension per minute, w = the rate of travel of the yarn in metres per minute and 1 = the required average opening length as herein defined in metres.

2. A method as claimed in claim 1, wherein air at from 20 to 25°C. under an initial pressure of from 2.5 to 5 atms. is used as the said medium.

3. A method as claimed in claim 2, wherein the initial pressure is from 3.2 to .2 atms. k.

A method as claimed in any one of the preceding claims wherein the yarn tension fluctuates between a lower value of from 0.02 to 0.18 and an upper value of from O. to 0.8.

5. A method as claimed in claim , wherein the upper yarn tension value is from 0.45 to Ο.63 p/den.

6. A method as claimed in claim or claim , wherein the lower yarn tension value is from 0.0k to 0.15 p/den.

7. A method as claimed in any one of the preceding claims, wherein the average frequency of the fluctuations in yarn tension is from 2000 to lOOOO/min.

8. A method as claimed in claim 75 wherein the average frequency of the f uctuations is from 5000 to 8500/min.

9. A method for producing an intertwined yarn, substantially as herein described with reference to the accompanying drawings and/or the Examples.

10. An apparatus for producing an intertwined yarn of predetermined average opening length, as herein defined, the apparatus comprising means for guiding the yarn to be treated; means for directing a jet of medium substantially perpendicularly to the yarn so that thereafter the medium flows freelj away; and means for subjecting the yarn to fluctuations in yarn tension, the frequency of the fluctuations being given by n = — ) where n = the number of cycles of fluctuations in tension per minute,, w = the rate of travel of the yarn in metres per minute and _1 = the required average opening length, as herein defined, in metres.

11 . An apparatus as claimed in claim 10 , comprising two delivery means arranged at a distance apar -;from one another, a blo\ving nozzle arranged before the second delivery means, and a means for generating the fluctuations in yarn tension arranged between the two supply means.

12. An apparatus as claimed in claim 10 or claim 11 , wherein the means for producing the fluctuations in yarn „ tension is an electromagnetic yarn brake.

13. An apparatus as claimed in claim 10 or claim 11 , wherein the means for producing the fluctuations in yarn tension is a deflector comprising of an eccentric driven by a variable-speed motor.

14. An apparatus as claimed in claim 6 , wherein an interference gear is arranged between the driving motor and the eccentric, the interference width of the interference gear amounting up to + 25 .

15 . An apparatus as claimed in claim 14, wherein the interference width amounts to from + 5f° to + 1 $ .

16. An apparatus for producing an intertwined yarn, substantially as herein described with reference to the accompanying drawings, and/or the